New bridges must be built to updated climate expectations, not past assumptions. Photo: NZTA / Waka Kotahi
- Documents from Waka Kotahi show the state highway network has 887 bridges that are more than 80 years old
- 17 of those are considered degraded enough to have speed or weight restrictions in place
- 6 of these are currently programmed for replacement
- 39 bridges on the state highway network are already past their 100th birthdays
- That doesn't include local bridges, which for some communities are the only route in or out
- A climate economist says it is crucial bridge replacements are built to survive the next big cyclone
With Cyclone Gabrielle bearing down on the East Coast, Tui Warmenhoven had to make a choice.
She could stay at Gisborne Hospital with her father, who had just suffered a severe heart attack, or return home to help her community at Ruatoria get through the coming storm, including her mother, who also had a heart condition.
"I left my dad with my brother and, unbeknownst to me, it was the last time I was going to see him, because he died. My nephew and my son ring me from the hospital, and they're crying."
By then, the storm had knocked out Hikuwai No.1 Bridge on State Highway 35, connecting Gisborne with Ruatoria.
Her son-in-law managed to get her to the funeral through the backroads, by clearing a path with a spade and a chainsaw.
"Big holes in the road, trees, mud, slash, it was just diabolical really and all the while trying to grieve," she says.
Hikuwai No.1 Bridge is being replaced as part of the cyclone clean-up, but Warmenhoven is more concerned about another one - Rotokautuku over the Waiapu river, which connects the northern part of her Ngāti Porou community with critical services in Ruatoria town.
That bridge was damaged in the cyclone and she said, if it was wiped out in the next big storm, half her community would have no access to medicine, shops, schools or first responders.
Official documents show 39 bridges on the state highway network are already past their 100th birthdays. By 2030, this number will increase to 260 bridges and by 2039 to 500 bridges.
Thirteen aged at least 50 - described in the documents as being "on life support" - have been prioritised for replacement by 2027 and Waka Kotahi has warned it will need more funding before 2030 to do further work. Otherwise, it warned the country would be faced with an "unrealistic" replacement programme.
Of the 887 bridges that are more than 80 years old, the agency told RNZ that 17 are considered degraded enough to have speed or weight restrictions in place.
Just six of these are currently programmed for replacement, less than one percent of the state highway network's octogenarian bridges. That doesn't include any ageing bridges that are off the state highway network, like Rotokautuku, which was built in 1964.
Climate economist Belinda Storey says building replacement bridges to withstand the next big cyclone is crucial.
"Because we've got a wave of bridges that are up for replacement, we've now got an opportunity to build them sufficiently resilient to withstand our future climate," she says.
"If we just rebuild them based on our old climate and our assumptions about how many extreme events we had under our old climate, we are setting them up to fail in the future."
Storey says the country's lack of preparedness for Gabrielle shows climate modelling used by the government is better at capturing averages than what scientists say are rapidly changing extremes.
She's says bridges on state highways aren't all that matter, when it comes saving lives.
"We expect that we're able to come to our neighbour's help," she says. "Outside the state highways, we've got bridges that might be the single route in to a community and they might be washed out."
Waka Kotahi says its design standards for new bridges allow for higher river levels with climate change, using environment ministry and council guidance.
"Bridge renewals and replacements are prioritised and programmed through the National Land Transport Programme (NLTP), which focuses on structures reaching the end of their serviceable life," it says. "The prioritisation process considers a range of factors, including asset condition, safety, function, and network importance, as well as the criticality of individual bridges."
The new Hikuwai bridge will be finished in mid-2026, while Rotokautuku was strengthened last year, as part of the cyclone recovery.
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